Drought and Climate for April 2017: Contiguous U.S. sees smallest area of drought since 2000

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By Deborah Bathke, NDMC Climatologist

Drought

Thanks to a very wet April, the May 2 U.S. Drought Monitor showed just 4.98 percent of the contiguous United States in drought. This was the smallest drought area depicted on the map since it began in 2000. According to the National Centers for Environmental Information, April 2017 ranked as the second wettest April in the 123-year period of record, largely because of much above average precipitation across the Mid-Atlantic, Mid-Mississippi Valley, Great Lakes, Central Plains, and Northwest. Most drought areas saw improvements, with the exception of the extreme southeastern United States and patches of north-central Texas, southeast Utah, the southern Arizona-New Mexico border, North Dakota, and Nebraska. During the month, the percentage of the contiguous United States experiencing drought (D1-D4) improved from 9.83 to 4.98 percent, moderate drought (D2) improved from 1.5 to 1.3 percent, and severe drought (D3) increased slightly, from 0.10 to 0.13 percent. Exceptional drought was not present. Drought continued in Hawaii while Alaska and Puerto Rico remained drought free.

Drought Outlook

The Climate Prediction Center’s May drought outlook calls for existing drought conditions to persist in the southern sections of California and Arizona as these regions enter the climatologically warm, dry summer season. Below-normal rainfall forecast for much of the Southeast is expected to result in the persistence of existing drought conditions and a deterioration of abnormally dry regions in southeastern Alabama, southern Georgia, South Carolina, and Florida. Seasonal precipitation favors the removal of remaining drought areas in the rest of the contiguous United States.

Temperatures

Temperatures were above normal in the eastern half of the country, with the National Centers for Environmental Information declaring that Delaware, Maryland, New Jersey, North Carolina, Ohio, Pennsylvania, West Virginia, and Virginia experienced their warmest April on record. Mean temperatures across these areas ranged from 6 to 8 degrees above average. In the western half of the country, near- to below-average temperatures were observed across the northern Plains, northern Rockies, Great Basin, and Northwest. Here, temperatures generally ranged from 0 to 4 degrees below average.

Precipitation

Above-average precipitation was observed across much of the United States. Heavy rains brought excess rainfall and flooding to the southern Plains, Mid-Mississippi River Valley, and Carolinas. The wettest areas received 200-400 percent of their average rainfall for the month of April.

Regional Overviews

Northeast

Warmer than normal temperatures dominated the entire Northeast during April. Temperatures ranged from 1 degree above normal in Maine to over 7 degrees above normal in Pennsylvania. Much of the Northeast also experienced above-normal precipitation, helping to ease many of the remaining drought conditions in the region. Overall, precipitation ranged from less than 50 percent of normal in Delaware to more than 200 percent of normal in western New York. At month’s end, only 3 percent of the region was experiencing drought, compared to 10.5 percent at the beginning of the month. Severe drought (D2) was eliminated and the region remained free of extreme (D3) and exceptional (D4) drought.

Southeast

Temperatures were much above average across the southeastern United States. Temperatures generally ranged from 5 to 9 degrees above normal northward of central Alabama and Georgia. Precipitation ranged from 2 inches below normal in Florida to a record wettest April in North Carolina, where departures of more than 7 inches above average were noted. Accordingly, the southern part of the region saw an expansion of drought conditions while the northern part saw improvements in drought. As a whole, drought decreased slightly, from 35.61 to 34.35 percent. Severe drought (D2) expanded over southern Georgia and Florida, increasing the percent area in this category from 9.05 percent to 12.97 percent. An introduction of extreme drought over Florida resulted in a slight increase in the region’s percent area in this category, from 1.08 to 1.32 percent.

Movers & Shakers for April 2017

State

Percent area April 4, 2017

Percent area May 2, 2017

Status

Percentage point change

Biggest increases in drought

Alabama

26.17

32.03

Severe

5.86

Florida

42.41

66.00

Moderate

23.59

13.01

39.42

Severe

26.41

0

5.53

Extreme

5.53

Georgia

29.94

56.83

Moderate

26.89

15.05

24.06

Severe

9.01

Biggest improvements in drought

Alabama

4.87

1.50

Severe

3.37

Arkansas

18.90

1.11

Moderate

17.79

Colorado

21.88

3.57

Moderate

18.31

3.03

0

Severe

3.03

Connecticut

74.81

24.06

Moderate

50.75

33.95

0

Severe

33.95

Georgia

4.16

1.11

Extreme

3.05

Hawaii

17.55

9.55

Severe

8.00

Illinois

6.05

0

Moderate

6.05

Kansas

10.41

0

Moderate

10.41

Louisiana

15.96

6.33

Moderate

9.63

Massachusetts

16.65

0.01

Moderate

16.64

Mississippi

9.58

5.08

Moderate

4.50

Missouri

12.73

0

Moderate

12.73

Nebraska

3.77

0

Moderate

3.77

New York

6.01

0

Moderate

6.01

North Carolina

36.05

0.25

Moderate

35.80

5.09

0

Severe

5.09

Oklahoma

14.50

0

Severe

14.50

Pennsylvania

11.56

7.64

Moderate

3.92

South Carolina

42.49

15.80

Moderate

26.69

15.41

0.15

Severe

15.26

South Dakota

16.62

0

Moderate

16.62

Tennessee

5.90

0

Moderate

5.90

Vermont

10.34

0

Moderate

10.34

Virginia

40.63

15.88

Moderate

24.75

Wyoming

9.33

0.12

Moderate

9.21

South

Above-average temperatures dominated most of the southern region, with departures ranging from more than 6 degrees above normal in Alabama and Tennessee to near normal in parts of Texas. Parts of eastern Oklahoma, Arkansas, and Louisiana observed more than 6 inches of rainfall above average April values. The wet weather alleviated drought and dry conditions across the area, leaving just 2.43 percent of the region in drought compared to 13.44 percent at the beginning of the month. Severe drought (D2) was eliminated and the region remained free of extreme (D3) and exceptional (D4) drought.

Midwest

Most of the Midwest was warmer than average in April. Departures ranged from 1 degree below normal in northwest Iowa to as much as 8 degrees above average in northern Ohio. Precipitation ranged from near normal in pockets of Minnesota, Iowa, Indiana, Ohio, and Kentucky to more than 12 inches above normal in southern Missouri. With the excess precipitation, drought was eliminated from the region.

West

Temperatures in the West ranged from 3 degrees below average in parts of the Pacific Northwest to 6 degrees above normal in southern California. Much of the Pacific Northwest was also wetter than normal, with coastal areas recording more than 6 inches above average April totals. Southern California and Arizona remained dry, with precipitation shortages near 1 inch. Overall, drought in the West decreased from 5.49 to 2.72 percent of the region. Moderate drought (D2) is now at 0.16 percent, down from 0.43 percent at the beginning of the month.

Alaska, Hawaii, and Puerto Rico

Alaska continued to remain drought free, though 33.01 percent of the state was experiencing abnormally dry conditions, up from 31.15 at the beginning of the month. In Hawaii, severe drought (D2) decreased from 17.55 to 9.55 percent, but the total area in drought remained constant, with 25.69 percent of the islands experiencing drought. Puerto Rico remained free from drought and abnormally dry conditions.

April 2017 impact summary: Florida sees wildfires and water shortages

Drought concerns ramped up in Florida, southern Alabama, and southern Georgia during April as the month was relatively dry, while drought eased in other parts of the county, thanks to abundant spring rains. Wildfire activity and water shortages were the main issues of concern for Floridians, who endured an unusually parched dry season. The state had 48 impacts in the Drought Impact Reporter, far more than any other state. At a distant second, California and North Carolina both had nine impacts, documenting California’s emergence from drought and North Carolina’s lingering drought, which was largely alleviated in April.

State of emergency declared in Florida

Governor Rick Scott declared a state of emergency for Florida on April 11 because of the multitude of wildfires burning in the parched state. Flames had scorched 250 percent more land in the first three months of 2017 than during the same time in 2016. On the morning of April 28, the Florida Forest Service reported 99 active wildfires in Florida scorching 28,621 acres, apart from the fires affecting 107,346 acres of federal land.

Water shortage warning issued for South Florida

A water shortage warning was issued by the South Florida Water Management District as the precipitation deficit continued to climb. Since November 1, precipitation in the district’s 16 counties has been 6.75 inches below normal, and the level of Lake Okeechobee has dipped to 12.04 feet. The district also prohibited fires on its lands and was preparing to close navigation locks on the north shore of Lake Okeechobee.

Lackluster dry season, dry shallow wells noted in southwest Florida

Florida’s dry season, which begins on November 1 and extends through May 31, brought 45 percent of normal rainfall for the southwest coast area of the South Florida Water Management District. This region was also seeing a rash of dry or inoperable shallow wells as the water table dropped for lack of rain to replenish it. In Lee County, 181 wells—149 domestic wells and 32 irrigation wells—have gone dry or are not working, according to Kurt Harclerode, operations manager for Lee County Natural Resources.

Fire near Georgia-Florida state line could burn for 6 months

A wildfire burning in the Okefenokee National Wildlife Refuge near the Georgia-Florida state line has charred more than 200 square miles and could continue to burn for the next six months, said fire officials. The fire, which was sparked by a lightning strike on April 6, grew rapidly in the parched swampland in the last days of April. The conflagration is expected to continue for several months and may not be extinguished or completely contained until November, unless a large storm event puts the fire out sooner.

Florida's wildlife feeling pinch of drought

Wildlife was also having a tough time with the dry conditions. Florida’s drying lakes and swamps were driving venomous snakes out of their normal habitat to seek more water somewhere else, sometimes bringing the serpents into people’s yards. In St. Petersburg, warm water in a fish pond resulted in the deaths of thousands of fish because warm water holds less dissolved oxygen than cool water does, causing fish to suffocate. The Florida Fish and Wildlife Conservation Commission received 50 calls on their fish kill hotline.

Deep snowpack in California means plentiful water allocations

The final snowpack measurement of the 2016-17 season on May 1 showed a snow-water equivalent (SWE) of 27.8 inches, or 190 percent of the historic average. Electronic measurements revealed the water content of the statewide snowpack was 42.5 inches, 196 percent of the May 1 average. The SWE of the northern Sierra snowpack was 39.9 inches (199 percent of average); the central and southern Sierra readings were 47.1 inches (202 percent of average) and 37.6 inches (180 percent of average), respectively. The annual precipitation tally begins with the start of the water year on Oct. 1.

Lake Oroville, the primary reservoir for the State Water Project (SWP), was at 91 percent of average, or 74 percent of its 3.5 million acre-foot capacity. In April, the Department of Water Resources increased its estimate of this year’s SWP supply to 100 percent of requests for contractors north of the Sacramento-San Joaquin Delta and 85 percent of requests for other contractors, the highest since the last full allocation in 2006.

Millions of trees dying in Southern California

Southern California is undergoing a massive tree die-off as the stress of drought, water restrictions, higher salinity levels in recycled water, wind, and new pests continues to take a terrible toll on the region’s trees, particularly those poorly suited to California’s climate.

One of the most affected native urban trees is the sycamore. An insect known as the polyphagous shot hole borer beetle is expected to kill all sycamore trees if the bug cannot be stopped. It is then expected to move on to destroy other tree species.